1. Field of the Invention
The present invention relates to a mobile communication system for use as a cellular system, a cordless telephone system, or a wireless LAN system, and more particularly to a technology for sharing hardware resources to meet different communication principles.
2. Description of the Related Art
Mobile communication systems offer various different communication services including a PHS (personal handyphone system), a PDC (personal digital cellular) system, a paging system, etc. It is expected that new services such as a high-speed wireless LAN system will be introduced into the market.
In mobile communication systems, information is transmitted via radio links between a base station and mobile stations, i.e., mobile communication units such as portable communication terminals. The conventional mobile communication systems need to provide a base station and mobile stations for each type of service which the mobile communication systems offer. This is because a dedicated set of hardware is required to realize to achieve a communication system for a certain communication service.
To receive a plurality of communication services, the user needs to own a plurality of different mobile stations, i.e., mobile communication units, corresponding to the respective communication services. However, owning many mobile stations is costly and makes the user feel awkward in selecting and using them. If the user wants to use a mobile station to receive a communication service overseas, then the user has to use a dedicated mobile station because the communication system which offers such a communication service overseas is different from available domestic communication systems. Therefore, the present mobile communication technology has presented an obstacle to a goal of achieving internationally accessible communication services.
Base stations that are available at present cannot handle new communication services which will be introduced because installation sites available are limited and the cost of installation is prohibitively high.
Japanese laid-open patent publication No. 7-222227 discloses a mobile communication unit which has both a device having a TDMA communication means and a device having a CDMA communication means. These different communication means are selected one at a time to enable the mobile communication unit to handle different communication schemes.
The disclosed mobile communication unit incorporates a plurality of hardware circuits based on different communication principles, or stated otherwise it is a combination of different mobile communication units. As a result, the mobile communication unit tends to be large in size and expensive, and fails to essentially solve the above problems.
According to the invention disclosed in Japanese laid-open patent publication No. 9-64601, some of a plurality of circuit elements of a high-frequency circuit in a radio communication unit are shared for all frequencies, and other circuit elements are connected to those same circuit elements depending on frequencies to be used, so that the single high-frequency circuit is capable of handling a plurality of frequencies.
Since the high-frequency circuit has the shared circuit elements and the circuit elements associated with the respective frequencies, the high-frequency circuit is liable to be large in size and expensive, and does not offer an essential solution to the above problems.
Heretofore, as described above, attempts to make one mobile communication unit adaptable to various different communication principles have necessarily resulted in an increase in size and cost, and devices or circuits based on those different communication principles need to be assembled in the mobile communication unit when it is manufactured.
It is therefore an object of the present invention to provide a mobile communication unit, a mobile communication system, a method of changing communication principles in a mobile communication system, and a base station which are capable of handling various different communication principles without involving increased unit size and cost.
In a mobile communication system for transmitting information between a base station and a mobile communication unit via a radio link, the base station transmits system software to the mobile communication unit via the radio link, and the mobile communication unit performs communication processing according to the received system software. Therefore, the same hardware resources are shared, but the communication principles of the mobile communication unit are changed by the system software. Specifically, using the hardware resources of the mobile communication unit as a platform, various system software downloaded from the base station into the platform is executed to adapt the single communication unit to various communication principles according to the system software. The system software is supplied from a center of communication services via a public exchange network to the base station, and then supplied from the base station to the mobile station present in the service area of the base station.
To change the communication principles of the mobile communication system, a radio communication means in the mobile communication unit receives a control program (system software) representing details of the communication processing from the base station via the radio link, and stores the received control program in a memory such as a RAM or the like. A control means comprising a CPU, a DSP, etc. then performs communication processing according to the control program stored in the memory.
Therefore, simply by transmitting various control programs from the base station via a radio link, it is possible to adapt the single mobile communication unit easily to various communication principles. The communication principles can be changed when required after the mobile communication unit has been manufactured.
If primary concern is given over user""s convenience for receiving various communication services, then it is preferable to supply various control programs from the base station via a radio link. The principles of the present invention are also applicable to providing new communication services at stores in view of user""s needs. In such a case, control programs may be supplied from a dedicated transmitter to the mobile communication unit via a radio link.
To change communication principles of the mobile communication system, a communication interface means of the base station receives system software from a center through a public exchange network, and a radio communication means of the base station transmits the system software received by the communication interface means via a radio link. In the mobile communication unit, a radio communication means receives system software from the base station via a radio link, a memory stores the control program received by the radio communication means, and a control means performs communication processing according to the control program stored in the memory.
Therefore, simply by transmitting various system software from the base station via a radio link, the mobile communication unit present in the service area of the base station can easily be adapted to various communication principles.
More specifically, when the mobile communication unit receives a control input of the user from an input means such as control buttons, a download requesting means transmits a download request for system software designated by the control input from the radio communication means via a radio link. In the base station, a system software supply means transmits system software according to the download request from the radio communication means via a radio link.
Therefore, the user can control the mobile communication unit to change communication processing of the mobile communication unit to desired details.
For making the user""s designating operation more convenient, the mobile communication unit comprises a menu requesting means for transmitting a menu request based on a control input from the user from the radio communication means via a radio link, and the base station comprises a menu providing means for transmitting a menu of system software that can be supplied in response to the menu request from the radio communication means via a radio link. The mobile communication unit further comprises output means for displaying the menu of system software received by the radio communication means, for the user to designate system software to be downloaded.
The radio communications relative to system software can be performed by effectively utilizing the traffic channel already provided for radio communications between the base station and the mobile communication unit. For example, a bidirectional control channel, together with a traffic channel for transferring user information, may be used between the base station and the mobile communication unit for transmitting the menu request, the menu, and the download request, and the system software via a radio link.
The radio communications relative to system software can be performed in another mode. The base station further comprises a system software supply means for successively and repeatedly transmitting a plurality of system software items from the radio communication means via a radio link, and the mobile communication unit further comprises an input means for receiving a control input from the user, and a memory control means for controlling the memory to store system software designated by the control input among the system software items received by the radio communication means, whereby communication processing can be performed by the system software designated by the user of the mobile communication unit.
When the user of the mobile communication unit selects one of the system software items that are successively transmitted from the base station, the user can easily change the communication processing of the mobile communication unit to desired details.
The radio communications relative to system software can be performed by effectively utilizing the traffic channel already provided for radio communications between the base station and the mobile communication unit. For example, a unidirectional broadcast channel from the base station to the mobile communication unit, together with a traffic channel for transferring user information, may be used for transmitting the system software via a radio link.
In a system for performing radio communications between the base station and the mobile communication unit using a traffic channel for transferring user information and a control channel provided together with the traffic channel, the radio communications relative to system software can be performed in the following mode:
In the mobile communication unit, an input means receives a control input from the user, and a change requesting means transmits a request to change system software designated by the control input from the radio communication means via a radio link using the control channel. In the base station, a channel selecting means selects and designates the traffic channel for transferring user information to transmit system software based on the request to change system software received by the radio communication means, a channel designating means transmits designating information of the traffic channel designated by the channel selecting means, from the radio communication means via a radio link using the control channel, and a system software supply means transmits system software changed in response to the request to change system software, from the radio communication means via a radio link using the traffic channel designated by the transmitted designating information. In the mobile communication unit, a memory control means controls the memory to store system software received by the radio communication means using the traffic channel designated by the designating information received by the radio communication means.
Alternatively, a system may not be designated by a changing request from the mobile communication unit, and the base station may cyclically transmit a plurality of system software items using a traffic channel designated thereby. In the mobile communication unit, system software designated by the input means among the system software received by the radio communication means using the traffic channel according to the designating information may be stored in the memory.
Since system software is transmitted via the traffic channel whose capacity is generally larger than the control channel, a considerably large system change can be made without undue efforts.
If the base station can be adapted to communication systems of different principles in the mode for transmitting system software using the broadcast and control channels, then broadcast and control channels corresponding to a plurality of communication systems of different principles are provided in a time-division multiplexed fashion between the base station and the mobile communication unit, and system software is transmitted from the base station to one of the mobile communication units via the broadcast and control channels which correspond to the one of the mobile communication units.
The present invention is also applied to a base station used in a mobile communication system. The base station receives a control program (system software) from a system management center or the like via a public exchange network, and the received control program is stored in a memory such as a RAM or the like. A control means comprising a CPU, a DSP, etc. performs communication processing according to the control program stored in the memory. By thus performing communication processing according to the control program received by the base station, the principles of radio communications between the base station and the mobile communication unit are changed according to the control program while sharing the same hardware resources.
Consequently, simply by transmitting various control programs via the public exchange network, it is possible to adapt the single base station easily to various communication principles. The communication principles can be changed when required after the base station has been manufactured and installed. Thus, the communication principles of a large number of installed base stations can easily be changed.